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btrfs: convert extent_map.refs from atomic_t to refcount_t

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refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Elena Reshetova
2017-03-03 10:55:12 +02:00
committed by David Sterba
parent 9b64f57ddf
commit 490b54d6fb
6 changed files with 12 additions and 11 deletions
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10
fs/btrfs/extent_map.c
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@@ -55,7 +55,7 @@ struct extent_map *alloc_extent_map(void)
em->flags = 0;
em->compress_type = BTRFS_COMPRESS_NONE;
em->generation = 0;
atomic_set(&em->refs, 1);
refcount_set(&em->refs, 1);
INIT_LIST_HEAD(&em->list);
return em;
}
@@ -71,8 +71,8 @@ void free_extent_map(struct extent_map *em)
{
if (!em)
return;
WARN_ON(atomic_read(&em->refs) == 0);
if (atomic_dec_and_test(&em->refs)) {
WARN_ON(refcount_read(&em->refs) == 0);
if (refcount_dec_and_test(&em->refs)) {
WARN_ON(extent_map_in_tree(em));
WARN_ON(!list_empty(&em->list));
if (test_bit(EXTENT_FLAG_FS_MAPPING, &em->flags))
@@ -322,7 +322,7 @@ static inline void setup_extent_mapping(struct extent_map_tree *tree,
struct extent_map *em,
int modified)
{
atomic_inc(&em->refs);
refcount_inc(&em->refs);
em->mod_start = em->start;
em->mod_len = em->len;
@@ -381,7 +381,7 @@ __lookup_extent_mapping(struct extent_map_tree *tree,
if (strict && !(end > em->start && start < extent_map_end(em)))
return NULL;
atomic_inc(&em->refs);
refcount_inc(&em->refs);
return em;
}